The present invention relates to a mechanism for applying ink to an ink roll of a printing press. The mechanism is of the type which includes an ink rail which extends partially circumferentially around the roll. A plurality of pumps pump the ink into a position to be picked up by the roll as it rotates relative to the ink rail. Each pump delivers ink to a circumferentially extending portion of the roll which corresponds to a column on the page to be printed. Numerous prior art patents disclose such inking mechanisms. Typical of such patents are U.S. Pat. Nos. 3,018,727; 3,134,326; 3,400,658 and 2,672,812.
Known ink rail designs are relatively heavy and cumbersome in construction. This is due to the fact that piston-type pumps are used commonly which have a stroke adjustment for purposes of adjusting the amount of ink which is delivered to the roll. Because of their weight, the pumps are commonly mounted off the ink rail which is generally manually removable from the press. Thus, relatively long conduits, or hoses, and fittings are necessary to deliver the ink to the roll.
In addition, piston-type pumps even if mounted on the ink rail deliver a pulsing flow of ink to the ink roll rather than a continuous even flow of ink. Also, the stroke adjustments are cumbersome, and relatively complicated mechanisms are involved. in a prior art structure utilizing a single gear pump to feed from a common header individual orifices each of which is equipped with a throttle pin to regulate flow, difficulty is experienced in controlling ink flow. This results because the flow through any one orifice will be affected by the settings at the other orifices of a given page pack. The present invention overcomes this problem and facilitates control of ink flow independently of the ink flow through adjacent or contiguous orifices in a given page pack. In the improved structures hereof, an ink supply is pressurized and individual motors respectively associated with individual gear pumps meter the ink from the supply.
Another disadvantage of known ink rail constructions is that a bead of ink tends to collect at the end of the ink rail. Periodically this bead of ink will release from the end of the ink rail and be carried through the inking train. As a result an excess of ink flows through the ink train and an adverse effect on the quality of the printing occurs.
In accordance with the present invention, a substantial simplification in structure is achieved along with improved inking of the roll. A plurality of ink pumps is associated with an ink rail and specifically are mounted directly on the ink rail. The ink pumps preferably are gear pumps, each having a D.C. motor associated therewith, and which, when operating, provide a continuous output flow of fluid. Each gear pump delivers ink to a particular section of the ink rail from which the ink is then applied to a particular circumferentially extending segment of the ink roll corresponding to a column on the page to be printed. By controlling the speed at which the motor operates, the amount of ink pumped can be varied and thus the amount of ink delivered to the roll can be varied. The motor speed can be controlled or shut off electrically over a broad range to provide accurate ink feed flow rates.
A plurality of gear pump and motor units are mounted in a spaced relation along the ink rail. Each pump has an inlet passage in the ink rail and an outlet passage also in the ink rail. The porting for the gear pump is face-type porting with the inlet and outlet passages in the ink rail intersecting a face of the ink rail against which the gear pump is assembled.
Further, in accordance with the present invention, the ink rail with the gear pumps and D.C. motors secured thereon, are supported on an ink rail support and may be manually removed from the ink rail support. The ink rail is removably secured to the ink rail support by a plurality of fasteners. When released from the ink rail support, the ink rail, along with the pumps and motors, may be removed as a unit since the assembly is relatively light weight.
Also in accordance with the present invention, the various gear pumps are assembled in so-called page packs, each of which corresponds to a page being printed in the printing press. Each page pack has a valve for delivering the same fluid to all of the gear pumps of the page pack. Along each inking roll there may be a plurality of page packs so that a plurality of different colored inks could be applied to the same roll at the same time. The valve associated with each page pack may be adjusted to deliver black ink to all of the gear pumps of the page pack, or to deliver colored ink to all of the gear pumps of the page pack. Also, for purposes of cleaning the ink roller and gear pumps, a cleaning solvent may be delivered through the valve to the ink roll. Accordingly, the valve has three inlets and one outlet which communicates with the gear pump through passages in the ink rail.
A problem which may be encountered when feeding several pumps from a single manifold conduit in the ink rail is starvation of those pumps remote from the ink inlet to the single manifold conduit. To overcome this problem, a preferred embodiment of the invention includes a large manifold chamber connected to the ink supply and individual conduits extending from the manifold chamber to each pump.
Further, the output of each gear pump is directed through an orifice located adjacent to the periphery of the ink roll. As the roll rotates past the orifice, ink is ripped out of the orifice and essentially is accelerated from zero speed to press speed. This action is believed to result in a heating of the ink and is believed to be a direct cause of the buildup of ink at the end of the ink rail in the prior art structures. It has been discovered that by providing a recess in the ink rail adjacent to the roller and which recess is located downstream of the orifice, the collection ink at the end of the ink rail is substantially minimized. It is believed that the recess gives the accelerated ink a chance to cool after it has been ripped from the orifice by the roll. As a result of this cooling, it has been found that buildup of ink on the end of the ink rail is minimized.
Experiments have shown that the average ink volume requirement on each column of a newspaper at a minimum press speed of 500 ft/min. is in the range of from 2-8 cc of ink/minute. For commercial application, flow requirements may be as low as 0.1 cc/min. per pump. Only one pump on the page pack of 8 pumps may be running at such a delivery rate. Others may be off entirely, or they may be running at a higher rate. The range required for commercial use is from 0.1 to 60 cc/min. Under such extreme requirements, a further problem occurs with D.C. drive motors for the pumps. With common D.C. motors driving the gear pumps for feeding the ink, the lowest reasonable speed is about 500 RPM. Below this value, the motor stalls or runs erratically and control is lost.
D.C. motors normally require a certain minimum voltage in order to begin running. To achieve the required range of ink delivery, accommodate variation in press speed on commercial offset presses, and provide minimum starting voltage, a pulsing circuit has been devised. Pulses of a predetermined width energize the motors, and the number of pulses per unit time is controlled by a press speed responsive voltage control oscillator. Each ink pump has, therefore, individual control as well as page control to increase or decrease ink supplies by 8 individual pumps normally feeding one printed page per block. Separate power supplies are desirably used for the pump drive and for the electronics to avoid noise spikes in the electronics. Remote electrical read out and control is available with the present improved system and not with the piston pump systems.